Presently many battery powered devices use operating voltage limits based on the battery chemistry of the rechargeable battery used to power the device. The voltage limits can establish, for example, a shutdown voltage threshold and a power up voltage threshold. A shutdown voltage threshold dictates the lowest battery voltage at which the battery should be operated, and when the battery voltage falls below the shutdown voltage threshold the device shuts down. Once shut down, the device will not power back up until the battery voltage rises above the power up voltage threshold, which typically requires charging the battery.
In conventional devices these limits are hard coded in the software of the device since battery technology has been fairly unchanged. However, more recently, various battery chemistries have been developed that provide benefits in capacity and operating voltage range. As such, it is desirable to not have fixed, or hard coded, voltage thresholds in the device.
It has long been conventional to include a memory device in rechargeable batteries. The memory device can contain data such as voltage thresholds and other battery information. The memory devices typically used in rechargeable batteries are “one wire” type devices that have a single wire for receiving, and transmitting data and commands in a serial fashion. Given that both a charger and the device powered by the rechargeable battery may need to access data in the memory device, there is a need for a method and apparatus that allows multiple masters to have access to battery data stored in a rechargeable battery.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.